ELECTRICAL DISCHARGE MACHINING OF HYBRID MATERIAL USING COPPER ELECTRODE AMIRUL AKMAL BIN MOHAMMAD YAZID UNIVERSITI TEKNOLOGI MALAYSIA

Transcription

1 ii ELECTRICAL DISCHARGE MACHINING OF HYBRID MATERIAL USING COPPER ELECTRODE AMIRUL AKMAL BIN MOHAMMAD YAZID UNIVERSITI TEKNOLOGI MALAYSIA

2 i ELECTRICAL DISCHARGE MACHINING OF HYBRID MATERIAL USING COPPER ELECTRODE AMIRUL AKMAL BIN MOHAMMAD YAZID A project report submitted in partial fulfilment of the requirements for the award of the degree of Master of Engineering (Mechanical-Advanced Manufacturing Technology) Faculty of Mechanical Engineering Universiti Teknologi Malaysia JUNE 2015

3 iii Bismillahirahmanirahim I strongly dedicated this project to my beloved father (Mohammad Yazid Bin Harun), mother (Faridah Bte Abdul Ghani) and my siblings (Helmi Husaini, Raimi Ruhaizat, Azrin Amirudin, Muhammad Hafeezudin and Leeqa Nurjannah), with their sincere prayers and endless support afforded me to successfully accomplish this thesis.

4 iv ACKNOWLEDGEMENT First and foremost, I would like to thank Allah Almighty for blessing and giving me strength to accomplish this thesis. Sincere appreciation to my supervisor Mr. Khidzir Bin Zakaria who constant support during my study at UTM and greatly helped me until this project completed. Other than that, the technicians who help me in completing the project, Mr.Aidid, Mr. Ali, Mr. Sazali, Mr. Rashid, Miss Norasikin and Mr. Salleh. Deepest gratitude to my beloved father, mother, brothers and sister and all of my family and friends for their real love, pray, spirit, continuous encouragement and patience within this study period.

5 v ABSTRACT In recent years, there has been a great of interest in copper alloy (FeCuSn) hybrid metal material due to several industrial applications. Extreme hardness and high brittleness properties of FeCuSn makes the machining of such material very difficult and time consuming, especially using traditional machining methods such as grinding and lapping techniques. Due to this, the cost of machining FeCuSn is very high. Despite high demand in electrical discharge machining (EDM) process by modern manufacturing industries, the mechanism of the process is quite complex. It is difficult to generate a model that can accurately correlate the input parameters with the responses. Optimum parameters play a significant role in increasing production rate and reducing the machining time. In this work, study on parametric optimization of surface roughness (Ra), material removal rate (MRR) and tool wear ratio (TWR) on die-sinking EDM of copper alloy (FeCuSn) was carried out. This study also establishes the models that relate the responses and the most significant design parameters like pulse-on time (Ton), discharge current (Ip) and servo voltage (SV) will be achieved. Full factorial design was applied to select the most influential design parameters. The experimental data was analyzed using the analysis of variance (ANOVA). The ANOVA results revealed that Ton, Ip and SV were the most influential parameters which affect the Ra, MRR and TWR. The optimum responses (Ra, MRR and TWR) were achieved through the optimum parameters setting predicted by the design expert software. The developed models were validated through confirmation runs, and the error between the experimental and predicted values of the responses lies within the acceptable limit.

6 vi ABSTRAK Aloi kuprum (FeCuSn) merupakan bahan besi hibrid yang semakin mendapat perhatian disebabkan kepelbagaian aplikasinya dalam industri. FeCuSn mempunyai sifat kekerasan dan kerapuhan yang amat tinggi menjadikan ia sukar untuk dimesin serta memerlukan masa yang lama, terutama apabila menggunakan kaedah pemesinan tradisional seperti teknik pengisaran dan pencanaian. Meskipun permintaannya dan kos yang tinggi dalam industri pembuatan termaju khasnya dalam proses electrical discharge machining (EDM) mekanisme untuk proses ini adalah kompleks. Ini disebakan kesukaran untuk menghasilkan model yang tepat dalam menghubungkaitkan kemasukan input dan respon dan ini memainkan peranan yang penting dalam peningkatan kadar pengeluaran dan pengurangan masa pemesinan. Kajian untuk mengoptimumkan parameter dari segi kekasaran permukaan (Ra), kadar pemotongan bahan (MRR) dan nisbah kehausan mata alat (TWR) untuk diesinking EDM bagi FeCuSn telah dijalankan dengan menghasilkan model yang berkaitan antara respon dan rekabentuk parameter utama seperti tempoh masa denyutan (Ton), arus puncak (Ip) dan voltan puncak (SV) akan diperolehi. Rekabentuk faktorial penuh adalah untuk menentukan rekabentuk parameter yang paling dominan. Permukaan tengah sentral bagi rekebentuk komposit telah digunakan untuk menentukan koefisien model bagi parameter terpilih dan akan dianalisiskan melalui analisis varians (ANOVA). Didapati bahawa Ton, Ip dan SV merupakan parameter yang paling ketara yang mempengaruhi Ra, MRR dan TWR. Manakala itu, respon optimum (Ra, MRR dan TWR) telah dicapai dengan menetapkan ramalan optimum parameter menggunakan perisian Design Expert. Model yang terhasil telah disahkan melalui ujian pengesahan sementara ralat antara eksperimen dan nilai ramalan bagi respon terletak dalam had boleh terima.

7 vii TABLE OF CONTENTS CHAPTER TITLE PAGE DECLARATION DEDICATION ACKNOWLEDGEMENT ABSTRACT ABSTRAK TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES LIST OF SYMBOLS LIST OF APPENDICES ii iii iv v vi vii x xii xv xvi 1. INTRODUCTION Project Background Problem Statement Objective of The Research Project Scope 3 2. LITERATURE REVIEW Electrical Discharge Machining (EDM) Die Sinking EDM Formation of Sparks Basic Principle of Die Sinking Parameter of Die Sinking EDM Pulse-On Time Pulse-Off Time 12

8 viii Electrical Discharge Peak Current Main Supply Voltage Servo Voltage Polarity Copper Electrode EDM Dielectric System Dielectric Fluid Types of Dielectric Fluids Powder Mixed Dielectric Fluid Tecniques For Proper Flushing of Dielectric Fluid Hybrid Material Copper Alloy (FeCuSn) Surface Integrity Surface Roughness Micro Cracks Recast Layer Design of Experiment (DOE) Full Factorial Design Analysis of Variance (ANOVA) METHODOLOGY Introduction Theory of The Experimental Design Two Level Full Factorial Design Machining Parameters Selection of Die-Sinking EDM Parameters Constant Machining Parameters Response Variables Material Removal Rate Tool Wear Ratio Surface Morphology Surface Roughness Experimental Set-Up and Procedure Machining Instruments Data Collection 42

9 ix 3.6. Data Analysis RESULTS AND DISCUSSION Introduction Experiment Results Analysis of Results Analysis Result of Surface Roughness Analysis Result of Material Removal Rate Analysis Result of Tool Wear Ratio Confirmation Runs Analysis of Surface Morphology Analysis of Recast Layer, RL Discussion Surface Roughness Material Removal Rate Tool Wear Ratio Image Analyzer Observation of EDMed FeCuSn Surface FESEM Obeservation of EDMed FeCuSn Rescast Layer CONCLUSIONS AND RECOMMENDATIONS Introduction Implication to the Industries Recommendation and Future Work 80 REFERENCES 81 Appendices A Appendices D 84-99

10 x LIST OF TABLES TABLE NO. TITLE PAGE 2.1 Typical copper electrode material prperty Definition of the major surface defect Design matrix of 2 3 full factorial design The analysis of variance (ANOVA) for the 2 3 factorial design Levels for screening of parameters using full factorial design Input parameters and level selected for the screening DOE Constant machining condotions Physical an mechanical properties FeCuSn Instrument for experiment Experimental plans Experimental results ANOVA for surface roughness ANOVA for material removal rate ANOVA for tool wear ratio Parameters and responses setting Optimum parameters setting Point prediction for optimum parameter setting Point prediction for optimum parameter setting Point prediction for optimum parameter setting 3 65

11 xi 4.11 Evaluation of surface in different parameter setting Evaluation of RL in different setting 68

12 xii LIST OF FIGURES FIGURE NO. TITLE PAGE 2.1 Spark Ignition in Die-Sinking EDM EDM Pulse Current Train for Controlled Pulse Generator Discharge Phenomenon in EDM Gap Variation of Voltage with Time Using an RC Generator Stages of Sparks in Die-Sinking EDM process Configuration of Die-Sinking EDM Die-Sinking EDM Parameters and Machining Performances Measures Principle of powder mixed EDM EDM Flushing Techniques Composition of two or more materials to developed hybrid materials Simulated section of various layers Surfsce texture festures TEM cross-sectional image and diffraction pattern of a monocrystalline silicon turned woth a single-point diamond tool Micrograph of flaking found at the base of a thread in the fractured bolt Surface layers division after EDM General model of a process Geometry view 2 3 factorial design Geometric presentation of contrasts corresponding to the main effects and interactions in the 2 3 factorial design 28

13 xiii 3.1 Overall step by step experimental methodology Cause and effect diagram Diagram of the experimental set-up Half-normal probability graph for surface roughness Normal plot of residuals for surface roughness Residuals versus predicted for surface roughness Outlier T for surface roughness Interaction graph of AC factors Main effect graph of A factors Main effect graph of B factors Main effect graph of C factors Cube graph of A, B and C factors Half-normal probability graph for material removal rate Normal plot of residuals for material removal rate Residuals versus predicted for material removal rate Outlier T for material removal rate Interaction graph of AB factors Interaction graph of AC factors Main effect graph of A factors Cube graph of A, B and C factors Half-normal probability graph for tool wear ratio Normal plot of residuals for tool wear ratio Residuals versus predicted for tool wear ratio Outlier T for tool wear ratio Main effect graph of A factors Main effect graph of B factors Cube graph for surface roughness of A, B and C factors 62

14 xiv 4.25 Image Analyzer micrograph on defect surface material according to significant factors for Ra and TWR Image Analyzer micrograph on defect surface material according to significant factors for MRR Effect of pulse-on time and servo voltage on Ra Effect of discharge current on Ra Effect of discharge current and pulse-on time on MRR Effect of discharge current and pulse-on time on TWR Image analyser showing micrographs of EDMed FeCuSn cross section surfaces by sinking-edm at Ton = 40 μs, Ip =4.4 A, SV =40 V Image analyser showing micrographs of EDMed FeCuSn cross section surfaces by sinking-edm at Ton = 10 μs, Ip =4.4 A, SV =100 V FESEM showing micrographs of EDMed FeCuSn cross section surfaces by sinking-edm at Ton = 40 μs, Ip =4.4 A, SV =40 V FESEM showing micrographs of EDMed FeCuSn cross section surfaces by sinking-edm at Ton = 40 μs, Ip =4.4 A, SV =40 V. 77

15 xv LIST OF SYMBOLS ANOVA DOE EDM Ip MRR Ra SR SV Ton TWR - Analysis of Variance - Design of Experiment - Electrical Discharge Machining - Peak Current - Material Removal Rate - Arithmetical Mean Roughness - Surface Roughness - Servo Voltage - Pulse-on Time - Tool Wear Ratio

16 xvi LIST OF APPENDICES APPENDIX TITLE PAGE Appendix A Master Project Gantt Chart 84 Appendix B Machined Workpiece and Electrode 87 Appendix C Image Analyser Micrograph For Machined Surface (20x Magnification) 89 Appendix D FESEM of EDMed FeCuSn Recast Layer At Variable Parameter Settings 96

17 1 CHAPTER 1 INTRODUCTION 1.1 Project Background The electrical discharge machining (EDM) is one of the major manufacturing processes widely applied in die and mold making industry to generate deep and three-dimensional complex cavities in many different classes of materials under roughing and finishing operations. The best supported theory to the explanation of electrical discharge machining process is the thermoelectric phenomenon and according to Van Dijck et al. (1974) and other researchers such as Zolotych (1955), Crookall and Khor (1974), Dibitonto et al. (1989) and König and Klocke (1997) the material removal in electrical discharge machining is associated with the erosive effect produced when spatially and discrete discharges occur between two electrical conductive materials. Sparks of short duration are generated in a liquid dielectric gap separating tool and workpiece electrodes. The electrical energy released by the generator is responsible to melt a small quantity of material of both electrodes by conduction heat transfer. Subsequently, at the end of the pulse duration a pause time begins and forces that can be of electric, hydrodynamic and thermodynamic nature remove the melted pools. In this study, EDM machining parameter is highlighted on the effect on the surface of work material of Iron-Copper-Tin (FeCuSn) hybrid metal material. Hybrid materials have been a great interest of researchers and manufacturing industries

18 2 nowadays because of its strengthening affect. Many of the researchers have developed much kind of material composition in order to fit its application in various field as stated earlier. Therefore it is crucial to provide optimum parameter setting for hybrid material specifically in EDM to machine such material closed to near net shape whilst maintaining its hardness. It is important to get near net shape component because it is relatively reduce cost, time, energy and may increase the production. In this case, only several parameters will be analysed and evaluated with design of experiment (DOE) method to optimize important parameters in this study in order to achieve the optimum quality surface of FeCuSn by EDM machining. 1.2 Problem Statement The electrical discharge machining (EDM) is the most famous manufacturing process due to its accuracy cutting, especially for intricate shapes and design, regardless of the material hardness being employed. A few problems are been highlighted, as the selection of machining parameters such as pulse-on time, pulseoff time, peak current and voltage in obtaining good cutting performance is still constricted against the cutting of materials. A part from that, there is no specific machining parameters for hybrid metal materials that can machine material close to near net shape specifically by EDM. Furthermore, the machining parameters are depending on the operator experiences. There are still needs to study, if the machining parameters have relationship with the surface quality or rates of material removal. In this study, various aspect of surface quality such as, surface roughness, surface finish and surface morphology are considered as a response variables for this study to evaluate the EDM parameters process during experimental work.

19 3 The aim of this project is to study the effect of machining parameter in EDM to determine optimum input parameters in obtaining a good surface quality, surface finish and surface morphology especially for FeCuSn hybrid metal material. 1.3 Objective of The Research The objective is crucial in providing a clear purpose and as a guide to the assessment strategies to achieve the goal of studies. There are two main objectives for this study, which are: (i) To analyse and evaluate of EDM cutting for FeCuSn hybrid metal material for precision cutting process in term of surface roughness, material removal rate and tool wear ratio (ii) To evaluate the input parameters of cutting process for FeCuSn hybrid metal material by EDM process. 1.4 Project Scope The scope of this experimental study is conducting a machining process by utilizing electrical discharge machining (EDM) which to analyze their cutting performance. The study will be focused upon the effect of the working surface and the surface morphology of work materials. The appropriate machining parameters such as pulse on time, pulse off time and peak current will be reset according to the Design of Experiment (DOE) while the other parameters remain constant. DOE analysis can help to optimize the machining processes by analyzing and evaluating the cutting performance. The material tested is FeCuSn hybrid metal material and utilizing the copper tungsten electrode as the electrode with the diameter of 10 mm.

20 4 After machining, the material will be evaluated using Surface Texture Machine, Research Microscope and Scanning Electron Microscope (SEM). Thus, from the obtaining results, the comparison will be made based on the surface morphology evaluation such as porosity, cracks formation and recast layer of FeCuSn. The results are then be analyze through Analysis of Variance (ANOVA) to determine the significant effect for every responses involved, in order to obtain high surface quality (SQ) and surface finish for FeCuSn. As a conclusion of this experiment, the guideline of FeCuSn hybrid metal material of EDM can be established.

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